Carbon-based nanostructures and films define a new class of engineered materials that display remarkable physical, photonic, and electronic properties. Graphene is a monolayer of sp2-bonded carbon atoms in a two-dimensional (2-D) structure. This layer of atoms can be wrapped into 0-D fullerenes, rolled into 1-D nanotubes, or stacked as in 3-D graphite. Graphene and carbon nanotubes (CNTs) exhibit unique electronic and photonic properties, high thermal conductivity, and exceptional mechanical properties. Diamond, comprised of sp3-bonded carbon atoms, is well known for its extreme hardness, high thermal conductivity, wide band gap, and large optical dispersion.
Recently, the discovery of graphene by micro-cleaving has generated intensive experimental research into its fabrication. Production methods that currently exist include ultrahigh vacuum (UHV) annealing of SiC, and chemical vapor deposition (CVD). Common techniques for CNT fabrication include plasma-arc discharge, laser ablation, and CVD. Methods for the synthesis of fullerenes include electrode-arc processes.
Although these methods have met with some success, they are not readily or economically scalable for large-area applications or may be subject to batch-to-batch inconsistencies. Combustion synthesis has demonstrated a history of scalability and offers the potential for high-volume continuous production at reduced costs. In utilizing combustion, a portion of the hydrocarbon gas provides the elevated temperatures required, with the remaining fuel serving as the hydrocarbon reagent, thereby constituting an efficient source of both energy and hydrocarbon reactant. This can be especially important as the operating costs for producing advanced materials, especially in the semiconductor industry, far exceed the equipment costs. Various morphologies of CNTs, carbides, and semiconducting metal-oxide and carbide nanowires have been produced using air-fuel combustion-based configurations, using both aerosol and supported-substrate methods.
The growth of these nanostructures and films over large areas remains especially challenging. Moreover, current processing methods can be complex, while still characterized by low growth rates and low total yield densities. Accordingly, it is evident that there is a strong need for better methods of synthesizing nanostructures, particularly carbon-based nanostructures.